Alexander50

Thanks for your help. I considered the electronic regulator, but was not fully satisfied because (1) there is no limit to the current the generator delivers and (2) I expected the regulator to get pretty hot because of the amount of power that is dissipated. So I used a mechanical voltageregulator as used on the 6 volt VW-beetle. Because I want to be able to convert it to original anytime, I did not change the groundconnection of the fieldcoil and left the third brush where it was. I used a powertransitor to invert the voltage on the fieldcoil. This transistor does not dissipate any power because it switches at the speed of the mechanical contact of the regulator. That contact hardly conducts any current (only the current to the basis of the transistor which is less than 1 Amp) so it will live forever. Because a third brush generator delivers only about -4 volt to build up the needed magnetic field, I used a resistor (about 1 ohm/5 Watt) to reduce the fieldvoltage from 6 volt to 4 volt. The transistor is connected to the ignitioncontact so the field gets full power even at idle. All these additional parts are fitted under the regulator so you can't see them. This solution limits the current from the generator at a safe level if the battery is exhausted. After starting the engine the generator starts immediately to charge even at idlespeed. The current is limited to approx 30 amps (which is the longtime limit for this gen) at low battery and reduces to approx 2 amps with a full battery. The transistor stays cold.The voltage is stabalized nicely on approx 7 volts at all speeds with a fully charged battery. I never could reach that situation with the third brush mode.

No balancingtube?

I looked for you at the site of Bob's Automobilia and they sell motormounts for the 1938. The link is: http://www.bobsautomobilia.com/cgi-bin/shop.pl/SID=1136470716.29890/page=product.html/product=79 at US$ 149 each. It appears to be a vulcanized rubber and not rubber sheets, so there is a greater difference between the 31 and 38 then I though. Never mind: you can get new ones.

Hi Guffin. I am interested in the schematics. If you would be so kind to email these to lexveen@hetnet.nl Thanx

So you dismantled it. A lot of work but the only way to find out. You talk about a "runout surface". Is the runout in an axial (in the line of the crankshaft) or radial (up and down) direction? I don't know which runout you mean, but how did you correct the runout with shims? If it is an axial runout and you put shims between the crankshaftflange and the flywheel you could get a lot of stress on the flange with the flange likely to crack. From the picture you can clearly see that the rubber in the motormounts is very bad. That gives a lot of vibration in the car! I really should renew that. The mounting seems to differ from the 1931 mounting but the principle will be the same: no metallic contact between the engine and the frame by using two rubber sheets. With this mounting the part that is connected to the flywheelhouse squeezes two rubber sheets on both sides of the part that is connected rigidly to the frame. I can only see one sheet, the other one should be on the other side of the framemounting. Maybe that one is missing. The bolts go all the way through but these should be kept on a distance with a spacerbushing so there is no metallic contact between the the engine and the frame.

There is a three brush 6 Volt generator in my car. These generators are regulated by interupting the field which is fed by the third brush. This third brush is between the two main brushes and is on a voltage of about half the generatorvoltage. The voltage on the third brush reduces when the current is increasing. A fully charged battery though leads to a high outputvoltage (up to 8 Volt) so the chargecurrent is too high and the battery is producing a lot of gas. The life of the battery and the bulbs is shortened. All connactions in the car are OK and the third brush is moved as far as possible to the earthed mainbrush, so it is working as intended within the limitations of this way of cargeregulation. I am not satisfied with this and want to regulate the generator with a normal voltageregulator, but connecting the filed to the normal regulator is not possible. The field of a generator that is intended to use with a normal voltageregulator is internally connected to the outputbrush. The field armature of the three brush generator has a much lower resistance and is internally connected to earth. I want to keep the generator as original as possible and dont want to rewind the fieldarmature or change the connections in the generator. Has anyone an idea how to use a regular voltageregulator without changing the generator ?

The carburetor of the flathead V8 Ford is far too small. The Ford has a displacement of 220 cid where this Buick has 310 cid. I tried the Ford carb and even with my smaller engine it strangled the engine at 45 mph. I put in the right one (see the picture) and it is easely doing 65 mph at half throttle. After running in the engine properly I guess it will run up to 80 mph. The size of the venturi is depending on the displacement. The formula is: the diameter of the venturi in milimeters is the square root of displacement in liters times rpm devided by the number of cylinders. So if you want too run this 309 cid engine at 2800 rpm without strangeling, the venturi should be the square root of 5,063 x 2800 / 6 which is 48,6 mm. The largest Ford carb of the thirties has a venturi of 1,25 inch (32 mm). That means the enginespeed is limited to 1300 rpm! Using one carb for less cilinders, for example the three carb layout, does not mean you can use proportinal smaller ones. If you use three carbs the venturi could be approx 20% smaller, in this case about 38 mm. As written before the problem is synchronisation and a possible instable idle. Allthough the single carb I am using gives a perfect running, it could even do better with a two stage carb (registercarb) where the second stage opens at about 40-50% of full throttle. With such a carb you have a good/better idle, very good torque at low speeds and enough breathing at higher rpm. This talk starts to sound like building a hotrod but it is still a normal conversion for the thirties. Buick experimented a lot with carbs and even the factory itself delivered carbmodifications for older models because there were too many complaints. So for the purists: this is acceptable allthough using a fifties carb is not right. Happy revving in 2006!

Nice pictures. Apparently we are not the only ones that are not happy with the original carburator, though I think the choice of the carb itself is not very good because it is not looking like a part used in that era.

60 viewers up to now but no one has one or knows one?

I know, but does anyone has experiences with the manifolds on the thirties Buick straight eights? For example: the small engine I have (1931 model 50) does not have bolts at the end of the manifold (next to cil 1 and 8) like the bigger brothers have. The manifold is not pressed against the head at these places. Does a steel manifold warp at these ends?

If that is the case it indicates that the vibration is caused by the primary shaft, so the problem is in the clutch/pressureplategroup or pilot bearing. The question is if the vibration that remains with the clutch disengaged is normal or not. Have you asked anyone familiar with Buicks of that age what his (or her) opinion is? Allthough it is a straight eight that is very smooth by nature there is allways some enginevibration. That vibration will be more noticable if the rubbers of the enginemountings are old.

ZondaC12, maybe some information about the influence of the compressionratio on the thermal efficiency=horsepower will help you. If you raise the ratio from 7:1 to 10:1 the efficiency will gain about 12%. The mechanical losses will raise too due to the increase in internal forces, so you could expect about 10-11% more horsepower. For 7:1 to 8:1 these figures are 4-5% and 7:1 to 9:1 about 7-8%. The gain is interesting but be sure the engine is healthy to cope with the higher forces. Before you do check the cranckshaft and rods for cracks. Check the bearings too. You will need a very good oilpressure to enjoy it for a longer time. Also advance the ignition to prevent detonation, because detonation gives enormous forces and will ruin the engine in short time.

I intend to change the castiron exhaustmanifold on my straight 8 1931 Model 54 by a welded steel one. Two reasons; I want to save the original castiron one because these are vulnerable for cracking and this one is still perfect, the other reason is that I think the cast iron manifold is basically a very bad design. The gasses of the rear cilinders collide with the gasses of the front cilinders so the efficiency of the engine is not good. I want to produce a steel manifold with two groups of four cilinders (1,2,7,8 and 3,4,5,6) go into two pipes that come together in one muffler. Because such changes are reversible it is not effecting the originality and value of the car. Who has experiences with such welded manifolds?

OK, I agree, that is a possible way to read it too and less work. English is not my native language so sometimes I make a mistake. Talking about that (only )oilleak: I wonder if the problem is the rear main seal or too much play in the bearing? Maybe it is an idea to remove the oilpan and the bearingcap and measure the play with plastigage. I don't have the limits for the 1938 but on the 1931 the play should not exceed 0,002 inch.

Replacing the rear main seal is not possible without taking the engine apart. You say that the engine is leaking everywhere. I would first clean the engine completely, then drive it for some time to see where the oil comes from. Sometimes the oil is coming from a spot at the front of the engine and blown al over by the fan. If that is not the case look further. I guess see oilleakage at the oilpan, oillines, valvecover and so? Most of these places can easely be solved, mostly gaskets that can be renewed without extensive disasseblies or joints that can simply be tightened. I do wonder if the oil is old or too thin? Or is the engine perhaps building up pressure due to a clogged or closed cranckcase vent?